springboot-2.2.5中自定义拦截器、静态资源映射、视图控制器和其他功能

在spring-boot-2.2.5中对MVC自动配置类进行的更改，之前的WebMvcConfigurerAdapter类声明为过时的，现在进行自定义扩展需要实现WebMvcConfigurer类重写其中的方法进行扩展

官方解释

If you want to keep those Spring Boot MVC customizations and make more MVC customizations (interceptors, formatters, view controllers, and other features), you can add your own @Configuration class of type WebMvcConfigurer but without @EnableWebMvc.
如果要保留这些Spring Boot MVC定制并进行更多的MVC定制（拦截器，格式化程序，视图控制器和其他功能），则可以添加自己的类型为WebMvcConfigurer的@Configuration类，但不添加 @EnableWebMvc。
注意：
1、扩展功能是添加配置类去实现 WebMvcconfigurer 类，springboot的自动默认配置同事生效
2、如果实现的是:WebMvcConfigurationSupport类，则springboot默认的自动配置类不生效
在总动配置类上有@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)注解
原理：

@Configuration(proxyBeanMethods = false)
@ConditionalOnWebApplication(type = Type.SERVLET)
@ConditionalOnClass({ Servlet.class, DispatcherServlet.class, WebMvcConfigurer.class })
@ConditionalOnMissingBean(WebMvcConfigurationSupport.class)
@AutoConfigureOrder(Ordered.HIGHEST_PRECEDENCE + 10)
@AutoConfigureAfter({ DispatcherServletAutoConfiguration.class, TaskExecutionAutoConfiguration.class,ValidationAutoConfiguration.class })
public class WebMvcAutoConfiguration {

创建MyMvcConfig类

addViewControllers：页面跳转

@Configuration
public class MyMvcConfig implements WebMvcConfigurer {@Overridepublic void addViewControllers(ViewControllerRegistry registry) {registry.addViewController("/success").setViewName("success");}
}

启动项目访问

addInterceptors：拦截器

1） addInterceptor：需要一个实现HandlerInterceptor接口的拦截器实例或者WebRequestInterceptor接口的实例

2）在实现了webMvcConfigur类的自定义配置类中重写addInterceptor方法，将自定义的拦截器进行注册

 addPathPatterns：用于设置拦截器的过滤路径规则；addPathPatterns("/**")对所有请求都拦截excludePathPatterns：用于设置不需要拦截的过滤规则
拦截器主要用途：进行用户登录状态的拦截，日志的拦截等。

先创建自定义的拦截器类MyIntercepter
自定义的interceptinterceptor可以实现HandlerInterceptor或者WebRequestInterceptor
然后将自定义的拦截器进行注册

public class MyMvcInterceptor implements HandlerInterceptor {@Overridepublic void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {System.out.println("afterCompletion");}/*** 这里是有一个返回值的，如果返回值为true，继续执行，如果返回值为false则不执行后续的操作* 这个方法在WebRequestInterceptor中则无返回值*/@Overridepublic boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {//ServletRequestUtils.getStringParameter(request,"ss");System.out.println("preHandle");return true;}@Overridepublic void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {System.out.println("postHandle");}
}

public class MyMvcRequestInterceptor implements WebRequestInterceptor {@Overridepublic void preHandle(WebRequest request) throws Exception {System.out.println("r----------preHandle");}@Overridepublic void postHandle(WebRequest request, ModelMap model) throws Exception {System.out.println("r----------postHandle");}@Overridepublic void afterCompletion(WebRequest request, Exception ex) throws Exception {System.out.println("r----------afterCompletion");}
}

在配置类中配置自定义拦截器及规则，使拦截器生效

 @Overridepublic void addInterceptors(InterceptorRegistry registry) {InterceptorRegistration interceptorRegistration = registry.addInterceptor(new MyInterceper()).addPathPatterns("/**").excludePathPatterns("/hello");}

addResourceHandlers：静态资源

springboot中默认的静态资源映射规则是通过url/webjars/** 去请求classpath:/WATE-INF/resources/webjars/下的内容.

WebMvcAutoConfiguration.java:中的默认规则如下：

@Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) {if (!this.resourceProperties.isAddMappings()) {logger.debug("Default resource handling disabled");return;}Duration cachePeriod = this.resourceProperties.getCache().getPeriod();CacheControl cacheControl = this.resourceProperties.getCache().getCachecontrol().toHttpCacheControl();if (!registry.hasMappingForPattern("/webjars/**")) {customizeResourceHandlerRegistration(registry.addResourceHandler("/webjars/**").addResourceLocations("classpath:/META-INF/resources/webjars/").setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));}String staticPathPattern = this.mvcProperties.getStaticPathPattern();if (!registry.hasMappingForPattern(staticPathPattern)) {customizeResourceHandlerRegistration(registry.addResourceHandler(staticPathPattern).addResourceLocations(getResourceLocations(this.resourceProperties.getStaticLocations())).setCachePeriod(getSeconds(cachePeriod)).setCacheControl(cacheControl));}}

如果我们需要自定义静态资源映射目录的话，只需重写addResourceHandlers方法即可。
addResoureHandler：指的是对外暴露的访问路径
addResourceLocations：指的是内部文件放置的目录

 @Overridepublic void addResourceHandlers(ResourceHandlerRegistry registry) {registry.addResourceHandler("/mySource/**").addResourceLocations("/my/");}

configureDefaultServletHandling：默认静态资源处理器

通过转发到Servlet容器的“默认” Servlet，配置一个处理程序以委派未处理的请求。常见的用法是将映射到“ /”，从而覆盖Servlet容器对静态资源的默认处理。。

@Override
public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {configurer.enable();configurer.enable("defaultServletName");

configureViewResolvers：视图解析器

重写此方法可以扩展视图解析器

   @Overridepublic void configureViewResolvers(ViewResolverRegistry registry) {InternalResourceViewResolver jspViewResolver = new InternalResourceViewResolver();jspViewResolver.setPrefix("/myJsp/");jspViewResolver.setSuffix(".jsp");jspViewResolver.setViewNames("*");registry.viewResolver(jspViewResolver);}